The invention relates to techniques to compare electronic documents.
Some computer application programs can compare two files based on the alphanumeric text contents. Applications that compare program source code generally compare two text files line-by-line. Only the text is analyzed whereas other file aspects, such as formatting, are ignored. Conventional word processing applications also compare different files or different versions of a file based only on their text contents.
Word processing applications increasingly produce content-rich files that integrate with text various objects, such as images, graphics, layout, color spaces, annotations, and so on. When such files are compared with the editing tools of the application programs, differences between the integrated objects are not detected, although such differences affect the appearance of a page on a display screen or on a printed page.